Ultrafast Infrared Spectroscopic Study of Microscopic Structural Dynamics in pH Stimulus-Responsive Hydrogels

Hydrogels show versatile properties and are of great interest in the fields of bioelectronics and tissue engineering.Understanding the dynamics of the water molecules trapped in the three-dimensional polymeric networks of the hydrogels is crucial to elucidate their mechanical and swelling properties at the molecular level.In this report,the poly(DMAEMA-co-AA)hydrogels were synthesized and characterized by the macroscopic swelling measurements under different pH conditions.Furthermore,the microscopic structural dynamics of pH stimulus-responsive hydrogels were studied using FTIR and ultrafast IR spectroscopies from the viewpoint of the SCN-anionic solute as the local vibrational reporter.Ultrafast IR spectroscopic measurements showed the time constants of the vibrational population decay of SCN-were increased from 14±1 ps to 20±1 ps when the pH of the hydrogels varied from2.0 to 12.0.Rotational anisotropy measurements further revealed that the rotation of SCNanionic probe was restricted by the three-dimensional network formed in the hydrogels and the rotation of SCN-anionic probe cannot decay to zero especially at the pH of 7.0.These results are expected to provide a molecular-level understanding of the microscopic structure of the cross-linked polymeric network in the pH stimulus-responsive hydrogels.

Photothermal and Chemotherapy Combined Therapy of B-CuS-DOX Based on/pH Dual Stimulation

Single chemotherapy is difficult to meet the needs of tumor cure. Photothermia combined with chemotherapy is anew and effective anti-tumor therapy. However, the drug loading of nanoparticles and increase in performance of photothermalconversion limits the therapeutic effect of combination therapy. In this study, two-dimensional boron (boron, B) nanoparticles wereprepared by ultrasonic exfoliation, and copper sulfide (CuS) nanoparticles and doxorubicin (DOX) were grown on the surface ofthe nanoparticles to form B-CuS-DOX nanoparticles. B-CuS carrier has high DOX drug loading capacity (864mg/g) and goodphotothermal conversion performance (photothermal conversion efficiency at 808nm is 55.8%). At the same time, it can achievedrug release and good photothermal response at near infrared and pH. The nanoparticles designed in this study are expected toprovide an effective chemotherapy-photothermal therapy strategy for tumor therapy in vivo.

Intelligent ion gels: Design, performance, and applications

Intelligent ion gels,which possess highly tunable mechanical,electrical,and stimulus‐responsive properties,have emerged as powerful candidates in the field of artificial intelligence,telemedicine,and health monitoring.To enrich the functionality of ion gels,it is critical to explore the link between the structure and function of ion gels.In this review,we provide an overview of the synthesis path and functional derivatives of ion gels.The conformational relationships of ion gels have been discussed,such as the effect of structure on electrical conductivity as well as sensing properties.From the perspective of stimulus response,the role of ion gels in areas such as bionic haptics,neural devices,artificial muscles,and intelligent displays has also been explored.It is possible that smart ion gels will open up a new horizon in the upcoming smart era,especially after the current challenges are resolved.

Advancements in the application of nanotechnology for the management of epileptic seizures

Epilepsy is a common yet complex neurological disorder.Historically,antiseizure medications(ASMs)have faced challenges in crossing the blood-brain barrier(BBB)and targeting the epileptogenic zone,creating a bottleneck in seizure management.Certain nanomaterials can facilitate drug penetration through the BBB and enable stimulus-responsive drug release,thereby enhancing targeted and efficient drug utilization while reducing adverse reactions in other brain tissues and peripherally.This article reviews the current researches on stimulus-responsive nanosystems applicable in antiepileptic therapy,as well as nanotechnology applications that improve the brain delivery of ASMs.

3D confined self-assembling of QD within super-engineering block copolymers as biocompatible superparticles enabling stimulus responsive solid state fluorescence

Eliminating colloidal toxicity and enabling its intrinsic fluorescence in aggressive environmental conditions are the key challenges for commercializing hydrophobic cadmium based quantum dots(QD).Polyarylene ether nitriles(PEN)are an example of super-engineering thermoplastics that possess a unique combination of thermal stability,intrinsic fluorescence,biocompatibility and distinct emulsion self-assembly feature.Herein,the co-self-assembly of amphiphilic PEN with hydrophobic CdSe@ZnS QD,confined in the three-dimensional(3D)oil-in-water emulsion droplets,has been explored tofabricate fluorescent microparticles(FMP).It was found that these FMP demonstrated good biocompatibility(cell viability above 90%),while exhibiting a fluorescence emission in aqueous solution that was retained(intensity retention ratio above 80%)within the whole pH range of 1-14,as well as,after being subjected to autoclaving at 120℃for 1 h.Interestingly,it was discovered that introduction of calcium ions in the emulsion self-assembly contributed to in-situ generation of phase changing nanoplates inside the FMP,which led to the photo-thermal modulated solid state fluorescence from drop-casted FMP film.Thanks to their versatile fluorescence,these FMP colloids were exploited as fluorescent probes for macrophages imaging,while micro-patterns with reversible changing of emission color were induced via thermal treatment and direct laser lithography.

High-temperature dielectric switch and second harmonic generation integrated in a stimulus responsive material

Stimulus re s ponsive materials can provide a variety of desirable properties in one equipment unit,such as optoelectronic devices,data communications,actuators,memories,sensors and capacitors.However,it remains a large challenge to design such stimulus responsive materials,especially functional materials having both dielectric switch and second harmonic generation(SHG).Here,a new stimuli-responsive switchable material [(CH_(3))_(3)N(CH_(2))_(2)Cl]_(2)]Mn(SCN)_(4)(H_(2)O)_(2)] was discovered as a potential secondharmonic generation(SHG) dielectric switch.It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions.In this work,we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation,which is tetramethylchloroethylamine(TMCEM) cation.By substituting H with a halogen,the increased steric hindrance of the molecular makes energy barrier increased,resulting in the reversible high-temperature phase transition.At the same time,the interactions of quasi-spherical cations and [Mn(SCN)_(4)(H_(2)O)_(2)]^(2-) anions affect a noncentrosymmetric structure to induce the SHG effect.These findings provide a new approach to design novel functional switch materials.

Electrochemiluminescence Sensor for Cancer Cell Detection Based on H_(2)O_(2)-Triggered Stimulus Response System

A H_(2)O_(2)-triggered stimulus response electrochemiluminescence(ECL)sensor for sensitive detection of cancer cells using mesoporous silica nanoparticles(MSNs)has been proposed.ECL signal-generating molecules(Ru(phen)32+)were encap-sulated into phenylboronic acid group-functionalized MSNs(PBA-MSNs)porous and capped by polyhydroxy functioned Au nanoparticles(AuNPs)through the interaction of carbohydrate-boronic acid first.Brunauer-Emmett-Teller(BET)and transmission electron microscopy(TEM)were applied to characterize the materials.The proposed controlled release sensing platform shows approximately no leakage from the mesoporrs of MSNs after a long time of storage.Cancer cells are initially incubated with the functionalized MSNs and then treated with ascorbic acid to endogenously produce H_(2)O_(2).Arylboronic esters in the MSNs surface can be oxidized by the produced H_(2)O_(2),causing the releasing of the molecule from MSNs and increased ECL signal.This technique displayed an excellent measurement for the breast cancer cells’sensitive diagnosis with a detection limit of 208 cells/mL.The phenomenon suggests that this sensing platform may be potentially applied for breast cancer sensitive detection in the future.

Excitation-wavelength-dependent fluorescent organohydrogel for dynamic information anti-counterfeiting

Anti-counterfeiting labels with various fluorescent colors are of great importance in information encryption-decryption,but are still limited to static information display.Therefore,it is urgent to develop new materials and encryption-decryption logic for improving the security level of secret information.In this study,an organohydrogel made up of poly(N,N-dimethylacrylamide)(pDMA)hydrogel network and polyoctadecyl methacrylate(pSMA)organogel network that copolymerized with two fluorophores,6-acrylamidopicolinic acid moieties(6APA,fluorescent ligand)and spiropyran units(SPMA,photochromic monomer),was prepared by a two-step interpenetrating method.As UV light of 365nm and 254nm can both cleave C_(spiro)-O bonds of SPMA,and the green fluorescence of 6APA-Tb^(3+) can only be excited by 254nm light,the organohydrogel displays yellow and red under the irradiation of 254nm and 365 nm,respectively.In addition to wavelength selectivity,these two fluorophores are thermal-responsive,leading to the fluorescence variation of the organohydrogel during heating process.As a result,secret information loaded on the organohydrogel can be decrypted by the irradiation of UV light,and the authenticity of the information can be further identified by thermal stimulation.Our fluorescent organohydrogel can act as an effective anti-counterfeiting label to improve the information security and protect the information from being cracked.

Self-assembly of artificial architectures in living cells-design and applications

Self-assembly exists widely in natural living system and artificial synthetic material system.Administration of self-assemblies of artificial architectures in living cells can be used to explore the molecular physicochemical fundamentals and operating mechanisms of living system,and consequently promote the development of biomedicine.In order to mimic naturally occurring self-assemblies and realize controllable functions,great efforts have been devoted to constructing dynamic assembly of artificial architectures in living cells by responding to intracellular specific stimuli,which can be used to regulate morphology,behaviors and fate of living cells.This review highlights the recent progress on artificial self-assembly in living cells.The molecular fundamentals and characteristics of intracellular environment that can induce the self-assembly of artificial architectures are introduced,and the representative work on dynamic artificial self-assembly in living cells is sketched chronologically.Moreover,intracellular stimuli-mediated pathways of artificial assembly in living cells are categorized,biological effects caused by intracellular self-assembly are summarized,and biomedical applications focusing on therapy and imaging are described.In the end,the perspective and challenges of artificial self-assembly in living cells are fully discussed.It is believed that the grand advances on artificial self-assembly in living cells will contribute to elaborating the molecular mechanisms in cells,and further promoting the biologically and medically-related applications in the future.

A TEMPERATURE AND pH DOUBLE SENSITIVE CHOLESTERIC POLYMER FILM FROM A PHOTOPOLYMERIZABLE CHIRAL HYDROGEN-BONDED ASSEMBLY

In this study, a novel H-bonded cholesteric polymer film responding to temperature and pH by changing the reflection color was fabricated. The H-bonded cholesteric polymer film was achieved by UV-photopolymerizing a cholesteric liquid crystal （Ch-LC） monomers mixture containing a photopolymerizable chiral H-bonded assembly （PCHA）. The cholesteric polymer film based on PCHA can be thermally switched to reflect red color from the initial green/yellow color as temperature is increased, which is due to a change in helical pitch induced by the weakening of H-bonded interaction in the polymer film. Additionally, the selective reflection band （SRB） of the cholesteric polymer film in solution with pH 〉 7 showed an obvious red shift with increasing pH values. While the SRB of the cholesteric polymer film in solutions with pH = 7 and pH 〈 7 hardly changed. This pH sensitivity in solutions with pH 〉 7 could be explained by the breakage of H-bonds in the cholesteric polymer film and the structure changes induced by --OH- and --K＋ ions in the alkaline solution. In contrast, it couldn＇t happen in the neutral and acidic solutions. The cholesteric polymer film in this study can be used as optical/photonic papers, optical sensors and LCs displays, etc.

Switching the emission of di(4-ethoxyphenyl)dibenzofulvene among multiple colors in the solid state

Luminescent materials exhibiting emission switching in the solid state have drawn much attention though there is still no clear design strategy for such materials. In this letter, we reported the crystallization induced emission enhancement (CIEE) of di(4-ethoxyphenyl)dibenzofulvene (1), and achieved switching its emission among four different colors through modulation of its molecular packing patterns. We have investigated its potential application as optical recording materials. The twisted conformations of CIEE compounds afford morphology dependent emission and facilitate tuning their emission through modulation of molecular packing patterns. Thus we provide a possible design strategy for solid stimulus responsive luminescent materials.

Dithienylethene metallodendrimers with high photochromic efficiency

It has been challenging to achieve multi-photochromic systems without affecting the individual photoswitching properties of the constituent units. Herein, we present the design and synthesis of a new family of platinum-acetylide dendrimers containing up to twenty-one photochromic dithienylethene(DTE)units that exhibit both high photochromic efficiency and individual switching properties. Upon irradiation with ultraviolet(UV) and visible(vis) light, the resultant metallodendrimers display high conversion yield and good fatigue resistance. More interestingly, cyclization-cycloreversion kinetics revealed that the photochromic property of each DTE unit in these metallodendrimers is unaffected by its neighbor and the full ring-closure of up to twenty-one DTE units in one single dendrimer has been achieved.

Deuteration triggered downward shift of dielectric phase transition temperature in a hydrogen-bonded molecular crystal

Deuteration of hydrogen-bonded phase transition crystals can increase the transition temperatures due to the isotope effect. But rare examples show the opposite trend that originates from the structural changes of the hydrogen bond, known as the geometric H/D isotope effect. Herein, we report an organic crystal, diethylammonium hydrogen 1,4-terephthalate, exhibits a reversible structural phase transition and dielectric switching. Structural study shows the cations reside in channels formed by one-dimensional hydrogen-bonded anionic chains and undergo an order-disorder transition at around 206 K. The deuterated counterpart shows an elongation of the O…O hydrogen bond by about 0.005 A. This geometric isotope effect releases the internal pressure of the anionic host on the cation guests and results in a downward shift of the phase transition temperature by 10 K.